Liquid crystal display, laminated polarizing plate and polarized light source device

ABSTRACT

This invention relates to a transmissive liquid crystal display including a light source (BL), a reflective linearly-polarizing layer (Pr 1 ), a birefringent layer (A) having specific optical properties and specific retardation properties, a light source-side absorptive linearly-polarizing layer (P 1 ), a liquid crystal cell (LC), and a viewer-side linearly-polarizing layer (P 2 ) which are arranged in this order. In the transmissive liquid crystal display of the invention, light leakage is suppressed in oblique directions so that black brightness can be reduced. A reduction in contrast in the normal direction can also be suppressed, which is caused by the distribution of light to the normal direction.

TECHNICAL FIELD

The invention relates to a transmissive liquid crystal display with highcontrast and reduced dark-state brightness and to a laminated polarizingplate and a polarized light source device each for use in such adisplay.

BACKGROUND ART

Transmissive liquid crystal display has a structure including twopolarizing plates with their absorption axes perpendicular to each other(namely arranged in cross Nicol) and a liquid crystal cell interposedbetween the two polarizing plates. Such liquid crystal displays have aproblem in which when viewed from oblique directions, they produce lightleakage so that they cannot produce black display, because the apparentangle between the absorption axes of the two polarizing plates is largerthan 90° when viewed from oblique direction. Particularly when thescreen is obliquely viewed at an azimuth angle of 45° with respect tothe absorption axes of the polarizing plates arranged in cross-Nicol,light leakage is significant.

A known method to solve such a problem includes placing an opticalcompensation layer of a retardation plate or the like between the twoorthogonal polarizing plates to change the polarization state, therebyreducing light leakage in oblique directions (see for example PatentDocuments 1 and 2). Even when using such an optical compensation layer,however, it has been difficult to completely prevent light leakage inoblique view. There is also another problem in which even though lightleakage is reduced using the optical compensation layer, light obliquelyincident on the liquid crystal cell can be refracted, reflected,diffracted, or scattered at the interface between various materials suchas TFT materials and antiglare layers constituting the liquid crystaldisplay, and part of the light can also be distributed to the normaldirection, so that contrast can be reduced not only in obliquedirections but also the normal direction.

Another method may also be applied which includes using a diffusingplate or the like in order to distribute leaked light in obliquedirections over a wide angle range (see for example Patent Document 3).However, such a method also distributes light to the normal directionwhere the contrast is originally high, so that the contrast in thenormal direction can be reduced. Therefore, such a method has littlepractical value.

Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No.04-305602

Patent Document 2: JP-A No. 04-371903

Patent Document 3: JP-A No. 2000-187205

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

In view of the above, an object of the invention is to provide atransmissive liquid crystal display in which black brightness is reducedby prevention of light leakage in oblique directions and in which areduction in contrast in the normal direction is also suppressed, whichis caused by the distribution of light to the normal direction, alaminated polarizing plate and a polarized light source device each foruse in the transmissive liquid crystal display.

Means for Solving the Problems

As a result of intense investigations, the inventors have found thatwhen a specific polarizing layer is placed on the light source side of atransmissive liquid crystal display, light obliquely incident on theliquid crystal cell is prevented so that the above problems can besolved, and have finally completed the invention. Specifically, theinvention is directed to a transmissive liquid crystal display includinga light source BL, a reflective linearly-polarizing layer Pr1, abirefringent layer A, a light source-side absorptive linearly-polarizinglayer P1, a liquid crystal cell LC, and a viewer-sidelinearly-polarizing layer P2 which are arranged in this order andsatisfy all the following conditions:

(a) the transmission axes of the reflective linearly-polarizing layerPr1 and the light source-side absorptive linearly-polarizing layer P1are arranged substantially parallel to each other;

(b) the birefringent layer has a thickness direction retardation Rthwhich satisfies the relation 250 nm≦Rth≦6000 nm; and

(c) of linearly polarized light emitted from the light source BL andtransmitted through the reflective linearly-polarizing layer Pr1, thebirefringent layer A makes substantially no change in the polarizationstate of linearly polarized light in the normal direction while thebirefringent layer A makes a change in the polarization state oflinearly polarized light in an oblique direction.

Furthermore, in the transmissive liquid crystal display of theinvention, it is preferred that the birefringent layer A has an in-planeretardation Re of from 10 nm to 100 nm, and the slow axis of thebirefringent layer A and the transmission axis of the reflectivelinearly-polarizing layer Pr1 are substantially parallel orperpendicular to each other. Further, in the transmissive liquid crystaldisplay of the invention, it is also a preferred constitution that thebirefringent layer A has an in-plane retardation Re of 20 nm or less.

Furthermore, in an embodiment of the transmissive liquid crystal displayof the invention, it is preferred that the birefringent layer A has anin-plane retardation Re and a thickness direction retardation Rth whichsatisfy the relation: 400 nm≦Rth−2×Re≦800 nm.

Furthermore, in the transmissive liquid crystal display of theinvention, it is preferred that the transmissive liquid crystal displayincludes a reflective linearly-polarizing layer Pr2 between thebirefringent layer A and the light source-side absorptivelinearly-polarizing layer P1 in such a manner that the light source-sideabsorptive linearly-polarizing layer P1 and the transmission axes areparallel to each other.

Furthermore, in the transmissive liquid crystal display of theinvention, it is preferred that the transmissive liquid crystal displayincludes a light diffusing layer between the birefringent layer A andthe light source-side absorptive linearly-polarizing layer P1 and/or onthe viewer side from the viewer-side linearly-polarizing layer P2.

Furthermore, in the transmissive liquid crystal display of theinvention, it is preferred that the reflective linearly-polarizing layerPr1, the birefringent layer A and the light source-side absorptivelinearly-polarizing layer P1 are integrally bonded to one another with apressure-sensitive adhesive.

The invention is furthermore directed to a laminated polarizing plateand a polarized light source device each for use in the transmissiveliquid crystal display.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an example of the cross-sectionalstructure of the transmissive liquid crystal display of the invention.

FIG. 2 shows an example of the placement angle of the respective layersof the transmissive liquid crystal display of the invention. Thetwo-headed arrow attached to each polarizing layer indicates thedirection of the transmission axis of the layer.

FIG. 3 is a schematic diagram showing an example of the basic mechanismin which the birefringent layer A maintains the intensity of light inthe normal direction incident on the liquid crystal cell, but it reducesthe intensity of light obliquely incident on the liquid crystal cell.

FIG. 4 is a schematic diagram showing an example of the cross-sectionalstructure of the transmissive liquid crystal display of the invention.

FIG. 5 shows an example of the placement angle of the respective layersof the transmissive liquid crystal display of the invention. Thetwo-headed arrow attached to each polarizing layer indicates thedirection of the transmission axis of the layer.

FIG. 6 is a schematic diagram showing an example of the basic mechanismin which a reflective linearly-polarizing layer Pr2 can enhance thelight recycling efficiency.

FIG. 7 is a schematic diagram showing an example of the cross-sectionalstructure of the transmissive liquid crystal display of the invention.

FIG. 8 is a schematic diagram showing an example of the cross-sectionalstructure of the transmissive liquid crystal display of the invention.

FIG. 9 is a view showing the viewing angle characteristics of each ofthe liquid crystal displays of Example 1 and before the addition of thebirefringent layer with respect to black brightness, white brightnessand contrast.

FIG. 10 is a graph showing the polar angle dependency of the blackbrightness of each of the liquid crystal displays of Example 1 andbefore the addition of the birefringent layer at an azimuth angle of 0°,in which the solid line indicates Example 1 according to the invention,and the broken line indicates the product before the addition of thebirefringent layer.

DESCRIPTION OF REFERENCE SYMBOLS

-   -   Pr1 reflective linearly-polarizing layer    -   Pr2 reflective linearly-polarizing layer    -   P1 light source-side absorptive linearly-polarizing layer    -   P2 viewer-side linearly-polarizing layer    -   A birefringent layer    -   BL light source    -   LC liquid crystal cell,    -   D1 light source-side light-diffusing layer    -   D2 viewer-side light-diffusing layer.

BEST MODE FOR CARRYING OUT THE INVENTION

The transmissive liquid crystal display of the invention includes alight source BL, a reflective linearly-polarizing layer Pr1, abirefringent layer A, a light source-side absorptive linearly-polarizinglayer P1, a liquid crystal cell LC, and a viewer-sidelinearly-polarizing layer P2 placed in this order.

The reflective linearly-polarizing layer Pr1 can transmit lightpolarized in a specific direction out of natural polarized light emittedfrom the light source and can reflect light polarized in a directionorthogonal thereto. Examples of the reflective linearly-polarizing layerPr1 which may be used include a grid polarizer, a multilayer thin filmlaminate including two or more layers of two or more materials differentin refractive index, a vapor-deposited multilayer thin film havingdifferent refractive indices, which is used for beam splitters and thelike, a birefringent multilayer thin film laminate including two or morebirefringent layers of two or more birefringent materials, and astretched resin laminate including two or more layers made of two ormore birefringent resins. Among them, the stretched resin laminateincluding two or more layers made of two or more birefringent resins asdisclosed in Japanese Patent Application National Publication(Laid-Open) No. 09-506837 is preferably used. For example, the productcommercially available under the trade name “D-BEF” from 3M Company maybe used as the reflective linearly-polarizing layer.

The birefringent layer A has the function of changing the polarizationstate of the linearly polarized light transmitted through the reflectivelinearly-polarizing layer Pr1. Although the mechanism to prevent lightleakage in oblique directions is described later, the birefringent layerA is required not to substantially change the polarization state oflight in the normal direction, namely the direction where the polarangle is Wand required to change the polarization state of light inoblique directions, namely directions where the polar angle is not 0°.In particular, the incident linearly-polarized light in a directionwhere light leakage can be significant in the transmissive liquidcrystal display is preferably converted into light linearly polarized ina direction orthogonal thereto by the birefringent layer A.

Here, in order not to convert the polarization state of the light in thenormal direction, the birefringent layer A should satisfy any one of thefollowing conditions: (i) it has a slow axis substantially parallel orperpendicular to the absorption axis of the reflectivelinearly-polarizing layer Pr1; and (ii) it has substantially no in-planeretardation, specifically has an in-plane retardation Re of 20 nm orless.

Further, in order to convert the polarization state of light in anoblique direction into linearly polarized light in a directionorthogonal thereto, the birefringent layer A should have a slow axis atan angle of 45° relative to the transmission axis of the reflectivelinearly-polarizing layer Pr1 and have a retardation of half awavelength (for example, a retardation of 275 nm at a light wavelengthof 550 nm), when viewed from the oblique direction. For example, inorder that light with an azimuth angle φ of 45° and a polar angle θ of60° which can cause most significant light leakage in a generaltransmissive liquid crystal display may be converted into linearlypolarized light in a direction orthogonal thereto, the birefringentlayer A to be used preferably has substantially no in-plane retardationand has a retardation in a range of 400 to 800 nm in its thicknessdirection. Here, while the phrase “substantially no in-planeretardation” means an in-plane retardation of 20 nm or less, asmentioned above, the in-plane retardation is more preferably 10 nm orless.

In practical liquid crystal displays, the angle dependency of lightleakage may vary with the type of the liquid crystal cell used, thepresence of optical films for compensating for the birefringence of theliquid crystal cell, or the like. Therefore, the optical properties ofthe birefringent layer A should be determined to be compatible with suchconditions. For example, when the liquid crystal cell is a twistednematic (TN) mode liquid crystal cell, a retardation of λ/2 ispreferably produced in an oblique direction as mentioned above, and inthis regard, the retardation in the thickness direction is preferablyfrom 250 nm to 1000 nm, more preferably from 300 nm to 900 nm, and evenmore preferably from 350 nm to 800 nm.

Further, in order that most significant light leakage at an azimuthangle φ of 45° and a polar angle A of 60° may be effectively preventedin a general transmissive liquid crystal display, as described above,the retardation that is determined when the birefringent layer isobserved from this direction is preferably half a wavelength,specifically about 275 nm at a light wavelength of 550 nm. From thesepoints of view, the in-plane retardation Re and the thickness directionretardation Rth preferably satisfy relation (1), more preferablyrelation (2), and even more preferably relation (3), as shown below.

400≦Rth−2×Re≦800  (1)

450≦Rth−2≦Re≦750  (2)

500≦Rth−2×Re≦700  (3)

In order to effectively prevent light leakage at an azimuth angle φ of45°, the in-plane retardation is preferably as small as possible. Incontrast, in order to effectively prevent light leakage at an azimuthangle φ other than 45°, the birefringent layer to be used may have acertain in-plane retardation. Such a retardation is preferably 100 nm orless, more preferably 90 nm or less, and even more preferably 80 nm orless, because a too high level of in-plane retardation can reduce theeffect of preventing light leakage in oblique directions, particularlyin the direction where φ is 45°.

On the other hand, when the liquid crystal cell is a vertically-aligned(VA) mode liquid crystal cell, the birefringent layer A preferably has athickness direction retardation of 500 nm to 6000 nm, more preferably of600 nm to 5000 nm, and even more preferably of 600 nm to 4000 nm, andthe in-plane retardation is preferably 20 nm or less, and morepreferably 10 nm or less. When the retardation is within the aboverange, the liquid crystal display on which black images are displayedcan be reduced in light leakage in oblique directions, and the screen onwhich white images are displayed can be prevented from coloration, whichis caused by retardation interference.

Here, in the specification, the in-plane retardation Re and thethickness direction retardation Rth are expressed as follows:Re=(nx−ny)×d, Rth=|(nx−nz)|×d, wherein nx is an in-plane refractiveindex in the slow axis direction of the birefringent layer, ny is arefractive index in the fast axis direction, nz is a refractive index inthe thickness direction, and d is the thickness of the birefringentlayer, and |(nx−nz)| is the absolute value of (nx−nz). Unless otherwisestated, Re and Rth are each a value at a measurement wavelength of 550nm.

Any materials or methods which can produce the characteristics describedabove may be used to form the birefringent layer A. Examples thereofinclude such as a layer of a cholesteric liquid crystal having aselective reflection wavelength outside the visible light region (380 nmto 780 nm) and having a fixed planar alignment, a layer of a rod-shapedliquid crystal having a fixed homeotropic alignment, a layer based on adiscotic liquid crystal having columnar or nematic alignment, a layerincluding an in-plane aligned crystal with negative uniaxiality, analigned polymer layer, an alignment film composed of a liquid crystalmaterial such as a liquid crystal polymer, a layer including an alignedlayer of a liquid crystal material supported on a film, and a layerproduced by appropriately stretching any of these materials.

The layer of a cholesteric liquid crystal having a fixed planaralignment preferably has a selective reflection wavelength in a regionoutside the visible light region in order to have no coloringabnormality in the visible light region with respect to a selectivereflection wavelength of a cholesteric liquid crystal. Hence, anecessity arises for a selective reflection light not to be in thevisible region. Selective reflection is specially determined by acholesteric chiral pitch and a refractive index of a liquid crystal. Avalue of a central wavelength in selective reflection may be in the nearinfrared region, whereas it is more desirably in an ultraviolet regionof 350 nm or less because of an influence of optical rotation exerted oroccurrence of a slightly complex phenomenon.

The layer of a rod-shaped liquid crystal having a fixed homeotropicalignment may be a liquid crystalline thermoplastic resin showing anematic liquid crystallinity at a high temperature; a polymerized liquidcrystal obtained by polymerizing a liquid crystal monomer and analignment agent, when required, under illumination with ionizingradiation such as an electron beam, ultraviolet or the like, or withheating; or a mixture thereof. While a liquid crystallinity may beeither lyotropic or thermotropic, a thermotropic liquid crystal isdesirable from the view point of ease of control and formability ofmonodomain. A homeotropic orientation is obtained for example in aprocedure in which a birefringent material described above is coated ona film made of a vertically aligned film (such as a film of a long chainalkylsilane) and a liquid crystal state is produced and fixed in thefilm.

As the layer using a discotic liquid crystal, there is available a plateobtained by producing and fixing a nematic phase or a columnar phase ina discotic liquid crystal material having an optically negativeuniaxiality such as a phthalocyanines or a triphenylene compounds eachhaving an in-plane spread molecule as a liquid crystal material.Inorganic layered compounds each with a negative uniaxiality aredetailed in a publication of JP-A No. 6-82777 and others.

The birefringent layer including an aligned polymer layer may beobtained by a method using an appropriate polymer material such aspolycarbonate, norbornene-based resin, polyvinyl alcohol, polystyrene,poly(methyl methacrylate), polypropylene or any other polyolefin,polyarylate, polyamide, or polyimide to form a polymer material solutionand applying the solution to a substrate to be aligned; a method ofstretching a film made of such a polymer material; a method of pressingsuch a polymer material; or a method of cutting from a crystallineproduct including such a polymer material aligned in parallel.

The in-plane retardation and the thickness direction retardation of thebirefringent layer may be adjusted by a known method such as coatingconditions, stretching conditions or adjustment of thickness.

The light source-side absorptive linearly-polarizing layer P1 to be usedmay be generally a polarizing plate including a protective film placedon one or both sides of the absorptive linearly-polarizing layer.

The absorptive linearly-polarizing layer to be used may be of any typewithout particular limitations. For example, the absorptivelinearly-polarizing layer may be a product produced by adsorbing adichroic material such as iodine or a dichroic dye on a hydrophilicpolymer film such as a polyvinyl alcohol-based film, apartially-formalized polyvinyl alcohol-based film, or apartially-saponified ethylene-vinyl acetate copolymer film anduniaxially stretching the film or may be a polyene-based aligned filmsuch as a dehydration product of polyvinyl alcohol or adehydrochlorination product of polyvinyl chloride or the like. Amongthem, a polarizing layer composed of a polyvinyl alcohol-based film anda dichroic material such as iodine is preferred. The thickness of thepolarizing layer is not particularly limited, and is generally about 5to about 80 μm.

For example, the polarizing layer including a uniaxially-stretchedpolyvinyl alcohol-based film dyed with iodine may be produce byimmersing a polyvinyl alcohol-based film in an aqueous iodine solutionto dye the film and stretching the film to 3 to 7 times the originallength. If necessary, the polyvinyl alcohol-based film may be immersedin an aqueous solution of potassium iodide or the like optionallycontaining boric acid, zinc sulfate, zinc chloride, or the like.Furthermore, if necessary, the polyvinyl alcohol-based film may beimmersed in water for washing, before dyeing. If the polyvinylalcohol-based film is washed with water, along with dirt on the surfaceof the polyvinyl alcohol-based film or an antiblocking agent can beremoved, and the polyvinyl alcohol film can be allowed to swell so thatunevenness such as uneven dyeing can also be effectively prevented.Stretching may be performed before, while or after dyeing with iodine.Stretching may also be performed in an aqueous solution of boric acid,potassium iodide or the like or in a water bath.

The transparent protective film placed on one or both sides of thepolarizing layer is preferably made of a material superior totransparency, mechanical strength, thermal stability, moisture barrierproperties, isotropy, or the like. Examples of polymers that may be usedto form the transparent protective film include polyester-based polymerssuch as polyethylene terephthalate and polyethylene naphthalate;cellulose-based polymers such as diacetylcellulose andtriacetylcellulose; acryl-based polymers such as poly(methylmethacrylate); styrene-based polymers such as polystyrene andacrylonitrile-styrene copolymers (AS resins); polycarbonate polymers; orthe like. Further, polyolefin having a structure of such aspolyethylene, polypropylene, and cyclo system- or norbornene;polyolefin-based polymers such as ethylene-propylene copolymers; vinylchloride-based polymers; amide-based polymers such as nylon and aromaticpolyamides; imide-based polymers; sulfone-based polymers;polyethersulfone-based polymers; poly(ether ether ketone)-basedpolymers; polyphenylene sulfide-based polymers; vinyl alcohol-basedpolymers; vinylidene chloride-based polymers; vinyl butyral-basedpolymers; arylate-based polymers; polyoxymethylene-based polymers;epoxy-based polymers; or blends of any of the above polymers. A curedlayer of thermosetting or ultraviolet-curable resin such as acryl-based,urethane-based, acrylic urethane-based, epoxy-based, or silicone-basedresin may also be formed as the transparent protective film.

Further, the protective film to be used may also be a polymer filmcontaining a resin composition containing a thermoplastic resin having asubstituted and/or unsubstituted imide group in the side chain and athermoplastic resin having a substituted and/or unsubstituted phenyl andnitrile groups in the side chain as disclosed in JP-A No. 2001-343529(WO01/37007); a polymer film containing a lactone ringstructure-containing (meth)acryl-based resin as disclosed in JP-A Nos.2000-230016, 2001-151814, 2002-120326, 2002-254544, 2005-146084, and2006-171464; a polymer film containing an acrylic resin having an alkylunsaturated carboxylate structure unit and a glutaric anhydridestructure unit as disclosed in JP-A Nos. 2004-70290, 2004-70296,2004-163924, 2004-292812, 2005-314534, 2006-131898, 2006-206881,2006-265532, 2006-283013, 2006-299005, and 2006-335902; a filmcontaining a thermoplastic resin having a glutarimide structure asdisclosed in JP-A Nos. 2006-309033, 2006-317560, 2006-328329,2006-328334, 2006-337491, 2006-337492, 2006-337493, and 2006-337569 orthe like. These films are preferred, because they have low retardationand low photoelastic coefficient so that they can avoid defects such asunevenness caused by polarizing plate distortion and because they havelow moisture permeability so that they can highly resistant to moisture.

The thickness of the protective film is appropriately determined, and isgenerally from about 1 to about 500 μm in view of strength, workabilitysuch as handleability, thin layer-forming properties, or the like. Inparticular, it is preferably from 1 to 300 μm, and more preferably from5 to 200 μm.

Further, the protective film is preferably as colorless as possible.Therefore, a protective film with a thickness direction retardation of90 nm or less is preferably used. The use of the protective film with athickness direction retardation of 90 nm or less can substantially avoidprotective film-induced coloration (optical coloration) of thepolarizing plate. The thickness direction retardation is more preferably80 nm or less, and particularly preferably 70 nm or less.

In view of polarizing properties, durability and on the like, acellulose-based polymer such as triacetylcellulose is preferably used asthe protective film. A triacetylcellulose film is particularlypreferred. Here, when the protective films are provided on both sides ofthe polarizing layer, the protective film to be used may be made of thesame polymer material or may be made of the different polymer materialon both sides.

Here, when the protective film on the reflective linearly-polarizinglayer Pr1 side has a retardation, the in-plane retardation and thethickness direction retardation of the birefringent layer A arepreferably adjusted in consideration of the value. Furthermore, thebirefringent layer A may be as the protective film on the reflectivelinearly-polarizing layer Pr1 side. Such a structure has both thefunctions of a protective film and a birefringent layer and is preferredin view of a reduction in the number of components or easiness ofoptical design.

The polarizing layer and the protective film are generally bondedtogether with an aqueous pressure-sensitive adhesive or the likeinterposed therebetween. Examples of the aqueous adhesive include suchas isocyanate-based adhesives, polyvinyl alcohol-based adhesives,gelatin-based adhesives, vinyl-based adhesives, latex-based adhesives,aqueous polyurethane adhesives, and aqueous polyester adhesives.

The reflection or absorption properties of the reflective or absorptivelinearly-polarizing layer vary with wavelength. Therefore, it isdifficult to produce completely neutral color. For example, theabsorptive linearly-polarizing layer containing iodine can have areddish brown hue due to its absorption properties. On the other hand,the retardation of the birefringent layer A varies with wavelength.Namely, the birefringent layer A has wavelength dispersion. Therefore,the birefringent layer A having a retardation of λ/2 (namely a phasedifference of n) at a certain wavelength converts incident linearlypolarized light into elliptically polarized light at wavelengths otherthan the certain wavelength, because the phase difference deviates fromn, while it can convert incident linearly polarized light into linearlypolarized light in a direction orthogonal thereto at the certainwavelength. At wavelengths other than the certain wavelength, therefore,light leakage can occur, which results in coloration. In thetransmissive liquid crystal display of the invention, the birefringentlayer may be used in such a manner that coloration due to the wavelengthdispersion of the birefringent layer can be complementary to colorationdue to the reflection or absorption properties of the reflective orabsorptive linearly-polarizing layer, so that the hue can be controlledto produce neutral color. The wavelength dispersion of the birefringentlayer may also be controlled by selecting the material to be usedtherein, or laminating two or more birefringent layers and thencontrolling by the methods described in such as JP-A Nos. 05-100114,05-27118 and 05-27119.

The transmissive liquid crystal display of the invention may have across-sectional structure and an arrangement of the respective layers asshown in FIGS. 1 and 2. In such a structure, light in the normaldirection can maintain its intensity when entering the liquid crystalcell, but light in oblique directions is reduced in intensity whenentering the liquid crystal cell, so that light leakage in obliquedirections can be suppressed. This mechanism is described below withreference to FIG. 3 by following conversion of the respective lightbeams in the normal direction and oblique directions.

(1) Part r1 of natural light supplied from the light source BL isperpendicularly incident on the reflective linearly-polarizing layerPr1.

(2) The reflective linearly-polarizing layer Pr1 transmits linearlypolarized light r3 and reflects linearly polarized light r2 in adirection orthogonal thereto.

(3) The linearly polarized light r3 passes through the birefringentlayer A. The birefringent layer A has a slow axis perpendicular orparallel to the polarization plane of the linearly polarized light r3,or the birefringent layer A has an in-plane retardation of substantiallyzero. Therefore, the polarization state of the linearly polarized lightr3 is not converted so that the birefringent layer A transmits linearlypolarized light r4.

(4) The direction of polarization of the linearly polarized light r4passing through the birefringent layer A is parallel to the direction ofthe transmission axis of the light source-side absorptivelinearly-polarizing layer P1. Therefore, it passes straight through thelight source-side absorptive linearly-polarizing layer P1.

(5) Linearly polarized light r5 passing through the light source-sideabsorptive linearly-polarizing layer P1 enters the liquid crystal cellplaced thereon and is transmitted without loss.

(6) On the other hand, part r11 of natural light supplied from the lightsource is obliquely incident on the reflective linearly-polarizing layerPr1.

(7) The reflective linearly-polarizing layer Pr1 transmits linearlypolarized light r13 and reflects light r12 linearly polarized in adirection orthogonal thereto.

(8) The linearly polarized light r13 passes through the birefringentlayer A and is converted into a polarization state which varies with theincidence angle. At a specific incidence angle, the birefringent layer Ahas a retardation of λ/2 and therefore transmits linearly polarizedlight r14 which is orthogonal to the linearly polarized light r13.

(9) The direction of polarization of the linearly polarized light r14passing through the birefringent layer A is perpendicular to thetransmission axis of the light source-side absorptivelinearly-polarizing layer P1. Therefore, it is absorbed by the lightsource-side absorptive linearly-polarizing layer P1.

(10) Thus, light in an oblique direction is not transmitted to theliquid crystal cell so that light leakage in the oblique direction canbe suppressed when black is displayed.

(11) The linearly polarized lights r2 and r12 are allowed to return tothe light source side and recycled. Therefore, light from the lightsource is efficiently used.

Furthermore, in the transmissive liquid crystal display of theinvention, it is also preferably configured to include a reflectivelinearly-polarizing layer Pr2 between the birefringent layer A and thelight source-side absorptive linearly-polarizing layer P1 in such amanner that the light source-side absorptive linearly-polarizing layerP1 and the transmission axes are parallel to each other. In this case,the cross-sectional structure and the arrangement of the respectivelayers may be as shown in FIGS. 4 and 5. When the reflectivelinearly-polarizing layer Pr2 is provided, the rate of recycling oflight from the light source can be enhanced so that white brightness isenhanced and contrast can be improved. An increase in the rate ofrecycling of light from the light source by means of having thereflective linearly-polarizing layer Pr2 is described with reference toFIG. 6, while conversion of light beams in the normal direction andoblique directions is followed.

(1) Part r21 of natural light supplied from the light source BL isperpendicularly incident on the reflective linearly-polarizing layerPr1.

(2) The reflective linearly-polarizing layer Pr1 transmits linearlypolarized light r23 and reflects linearly polarized light r22 in adirection orthogonal thereto.

(3) The linearly polarized light r23 passes through the birefringentlayer A. The birefringent layer A has a slow axis perpendicular orparallel to the polarization plane of the linearly polarized light r23,or the birefringent layer A has an in-plane retardation of substantiallyzero. Therefore, the polarization state of the linearly polarized lightr3 is not converted so that the birefringent layer A transmits linearlypolarized light r24.

(4) The direction of polarization of the linearly polarized light r24passing through the birefringent layer A is parallel to the direction ofthe transmission axis of the reflective linearly-polarizing layer Pr2.Therefore, it transmits linearly polarized light r25.

(5) The direction of polarization of the linearly polarized light r25 isparallel to the direction of the transmission axis of the lightsource-side absorptive linearly-polarizing layer P1. Therefore, itpasses straight through the light source-side absorptivelinearly-polarizing layer P1.

(6) Linearly polarized light r26 passing through the light source-sideabsorptive linearly-polarizing layer P1 enters the liquid crystal cellplaced thereon and is transmitted without loss.

(7) On the other hand, part r31 of natural light supplied from the lightsource is obliquely incident on the reflective linearly-polarizing layerPr1.

(8) The reflective linearly-polarizing layer Pr1 transmits linearlypolarized light r33 and reflects light r32 linearly polarized in adirection orthogonal thereto.

(9) The linearly polarized light r33 passes through the birefringentlayer A and is converted into a polarization state. In this process, ata specific incident angle, linearly polarized light r34 which isorthogonal to the linearly polarized light 33 is transmitted, becausethe birefringent layer A has a retardation of λ/2.

(10) The direction of polarization of the linearly polarized light r34passing through the birefringent layer A is perpendicular to thedirection of the transmission axis of the reflective linearly-polarizinglayer Pr2. Therefore, it cannot pass through the reflectivelinearly-polarizing layer Pr2 but is reflected as linearly polarizedlight r35.

(11) Based on the same mechanism as described in article (3) above, thebirefringent layer A transmits linearly polarized light r36 which isorthogonal to the linearly polarized light r35.

(12) The direction of polarization of the linearly polarized light r36is parallel to the direction of the transmission axis of the reflectivelinearly-polarizing layer Pr1. Therefore, the layer Pr1 transmitslinearly polarized light r37, which is allowed to return to the lightsource side and to be recycled. Furthermore, the linearly polarizedlights r22 and r32 are similarly allowed to return to the light sourceside and recycled. Therefore, light from the light source is efficientlyused.

(13) When the reflective linearly-polarizing layer Pr2 is provided, notonly the linearly polarized light r22 and r23 reflected from thereflective linearly-polarizing layer Pr1 to the light source side butalso linearly polarized light r37, which is part of the light oncetransmitted through the reflective linearly-polarizing layer Pr1, arerecycled so that the light recycling rate can be enhanced.

In the transmissive liquid crystal display of the invention, a lightsource-side light-diffusing layer D) may be provided between thebirefringent layer A and the viewer-side linearly-polarizing layer P1 asshown in FIG. 7 in order to prevent rainbow-like unevenness on thescreen, which is caused by Newton's rings. In view of contrastenhancement, the light source-side light-diffusing layer D1 that may beused preferably resists depolarization and furthermore preferablyexhibits less back scattering. For example, it may be provided as alight-diffusing pressure-sensitive adhesive layer. A layer in whichparticles having different refractive index are mixed into thepressure-sensitive adhesive is effectively used as the light-diffusingpressure-sensitive adhesive layer. For example, a fine particledispersion type diffusing member as disclosed in JP-A Nos. 2000-347006and 2000-347007 is preferably used. Furthermore, a transparent film(resin) containing particles with a refractive index different from thatof the resin, a hologram sheet, a microprism array, a microlens array,or the like may also be used.

The respective layers may be simply placed on one another to form alaminate. In view of workability and light use efficiency, therespective layers are preferably bonded to one another with an adhesiveor a pressure-sensitive adhesive to form a laminate. In this case, theadhesive or the pressure-sensitive adhesive is preferably transparent,preferably shows no absorption in the visible light range, andpreferably has a refractive index as close as possible to that of eachlayer, in view of suppressing surface reflection. From this point ofview, for example, acryl-based pressure-sensitive adhesives or the likeare preferably used. Furthermore, the diffusing pressure-sensitiveadhesive layer described above, in which particles having differentrefractive index are mixed into the pressure-sensitive adhesive, mayalso be used.

If necessary, particles for controlling the diffusion degree can beadded to impart isotropic scattering properties, or an ultravioletabsorbing agent, an antioxidant, a surfactant for imparting levelingproperties for film production or the like may be appropriately added toeach layer and the adhesive layer or the pressure-sensitive adhesivelayer. The liquid crystal display may be formed according toconventional techniques. Specifically, the liquid crystal display may begenerally formed by appropriately assembling the liquid crystal cell,polarizing plates or optical films, and optional components such as alighting system and incorporating a drive circuit. In the invention, theliquid crystal display may be formed according to conventionaltechniques without particular limitation, except that the reflectivelinearly-polarizing layer Pr1, the birefringent layer A and the lightsource-side absorptive linearly-polarizing layer P1 are placed betweenthe liquid crystal cell and the light source in such a manner that theconditions described above are satisfied.

Examples of a liquid crystal cell used in the liquid crystal displayinclude various liquid crystal cells such as twisted nematic (TN) mode,supertwisted nematic (STN) mode, homogeneous alignment (ECB) mode,vertical alignment (VA) mode, in plane switching (IPS) mode, fringefield switching (FFS) mode, bend nematic (OCB) mode, hybrid alignment(HAN) mode, ferroelectric liquid crystal (SSFLC) mode, andantiferroelctric liquid crystal (AFLC) mode liquid crystal cells. Amongthem, it is preferable to use the retardation film and the polarizingplate of the present invention, by combining, in particular, with TNmode, VA mode, IPS mode, OCB mode, FFS mode, and OCB mode liquid crystalcells. Most preferably, a retardation film and the polarizing plate ofthe present invention are used by combining with an IPS mode or FFS modeliquid crystal cell.

As backlight, direct under-type backlight, sidelight-type backlight, andplanner light source can be used. In addition, a reflecting plate can beused with backlight. Further, upon formation of a liquid crystaldisplay, one or more layers of an appropriate part such as a diffusionplate, an antiglare layer, a reflection preventing membrane, aprotecting plate, a prism array, a lens array sheet, and a lightdiffusion plate can be arranged at an appropriate position.

The viewer-side linearly-polarizing layer P2 may be placed on the viewerside of the liquid crystal cell in such a manner that the transmissionaxes of the viewer-side linearly-polarizing layer P2 and the lightsource-side absorptive linearly-polarizing layer P1 are substantiallyperpendicular to each other. The viewer-side linearly-polarizing layerP2 to be used is preferably an absorptive linearly-polarizing layer andan absorptive linearly-polarizing layer having a protective film on oneor both sides thereof is generally used, similarly to the lightsource-side absorptive linearly-polarizing layer P1. The viewer-sidelinearly-polarizing layer P2 to be used may be the same as or differentfrom the light source-side absorptive linearly-polarizing layer P1.

A hard coat layer may be prepared, or antireflection processing,processing aiming at sticking prevention, diffusion or anti glare may beperformed onto a face of the protective film on which the polarizinglayer has not been adhered.

A hard coat processing is applied for the purpose of protecting thesurface of the polarizing plate from damage, and this hard coat film maybe formed by a method in which, for example, a curable coated film withexcellent hardness, slide property etc. is added on the surface of theprotective film using suitable ultraviolet curable type resins, such asacrylic type and silicone type resins. Antireflection processing isapplied for the purpose of antireflection of outdoor daylight on thesurface of a polarizing plate and it may be prepared by forming anantireflection film according to the conventional method etc. Besides, asticking prevention processing is applied for the purpose of adherenceprevention with adjoining layer.

In addition, an anti glare processing is applied in order to prevent adisadvantage that outdoor daylight reflects on the surface of apolarizing plate to disturb visual recognition of transmitting lightthrough the polarizing plate, and the processing may be applied, forexample, by giving a fine concavo-convex structure to a surface of theprotective film using, for example, a suitable method, such as roughsurfacing treatment method by sandblasting or embossing and a method ofcombining transparent fine particle. As a fine particle combined inorder to form a fine concavo-convex structure on the above-mentionedsurface, transparent fine particles whose average particle size is 0.5to 50 μm, for example, such as inorganic type fine particles that mayhave conductivity comprising silica, alumina, titania, zirconia, tinoxides, indium oxides, cadmium oxides, antimony oxides, etc., andorganic type fine particles comprising cross-linked of non-cross-linkedpolymers may be used. When forming fine concavo-convex structure on thesurface, the amount of fine particle used is usually about 2 to 50weight part to the transparent resin 100 weight part that forms the fineconcavo-convex structure on the surface, and preferably 5 to 25 weightpart. An anti glare layer may serve as a diffusion layer (viewing angleexpanding function etc.) for diffusing transmitting light through thepolarizing plate and expanding a viewing angle etc.

In addition, the above-mentioned antireflection layer, stickingprevention layer, diffusion layer, anti glare layer, etc. may be builtin the protective film itself, and also they may be prepared as anoptical layer different from the protective film.

In the transmissive liquid crystal display of the invention, aviewer-side light-diffusing layer D2 is preferably placed on the viewerside from the viewer-side linearly-polarizing layer P2 as shown in FIG.8 in order to enhance white brightness in oblique directions and toexpand the viewing angle. The viewer-side light-diffusing layer D2 maybe formed by a method of laminating a light scattering plate, a hologramsheet, a microprism array, a microlens array, or the like as anindependent optical layer, by a method of imparting the diffusingfunction to the antiglare layer, or the like. Among them, alight-diffusing layer with substantially no back scattering ispreferred, and, for example, a light scattering plate with a haze of 80%to 90% as disclosed in JP-A Nos. 2000-347006 and 2000-347007 ispreferably used. Further, in view of reducing variations in viewingangle characteristics with azimuth angle and producing uniform display,an anisotropic light-scattering film as disclosed in such as JP-A No.2000-171619 may also be used.

In the transmissive liquid crystal display of the invention, an opticalfilm which is made of various polymer materials, liquid crystalmaterials or the like may also be used as an optical compensation layerfor the purpose of enhancing image quality. Such an optical compensationlayer may be placed between the light source-side absorptivelinearly-polarizing layer P1 and the liquid crystal cell and/or betweenthe viewer-side linearly-polarizing layer P2 and the liquid crystalcell. The optical compensation layer may be appropriately selecteddepending on the mode of the liquid crystal cell (such as TN, VA, OCB,or IPS).

A material or a method for producing such an optical compensation layeris not particularly limited, and examples include a layer of acholesteric liquid crystal having a selective reflection wavelengthoutside the visible light range (380 nm to 780 nm) and having a fixedplanar alignment, a layer of a rod-shaped liquid crystal having a fixedhomeotropic alignment, a layer based on a discotic liquid crystal havinga columnar or nematic alignment, a layer including an in-plane alignedcrystal with negative uniaxiality, an aligned polymer layer, an alignedfilm composed of a liquid crystal material such as a liquid crystalpolymer, a layer including an aligned layer of a liquid crystal materialsupported on a film, and a layer produced by appropriately stretchingany of these materials. Further, a laminate of two or more of theselayers may also be used.

EXAMPLES

The invention is more specifically described herein below with referenceto examples, however, the invention is not intended to be limit toexamples described below.

Here, the in-plane retardation Re and the thickness directionretardation Rth were determined as described below.

The retardation of the film in the normal direction and the retardationof the film inclined by 40° with respect to the slow axis were measureat a wavelength of 550 nm using an automatic birefringence measuringdevice (automatic birefringence analyzer “KOBRA 21ADH” manufactured byOji Scientific Instruments). These values were used to calculate therefractive index nx of the film in a direction where the in-planerefractive index is maximum, the refractive index ny of the film in adirection perpendicular thereto, and the refractive index nz of the filmin its thickness direction. The in-plane retardation (nx−ny)×d and thethickness direction retardation (nx−nz)×d were calculated from thesevalues and the thickness d.

Here, when the retardation of the birefringent layer was measured, thelayer was separated from the substrate and then transferred onto a glassplate with a pressure-sensitive adhesive in order to avoid the effect ofthe birefringence which the substrate has.

Application to TN Mode Liquid Crystal Cell Example 1

A coating solution was prepared by adjusting and blending aphotopolymerizable nematic liquid crystal monomer (PalioColor LC-242(trade name) manufactured by BASF), a chiral agent (“PalioColor LC-756”(trade name) manufactured by BASF), a photopolymerization initiator(“Irgacure 906” (trade name) manufactured by Ciba Specialty ChemicalsInc.), and a solvent (cyclopentanone) in such a manner that theselective reflection wavelength was 350 nm. The coating solution wasapplied to a biaxially-stretched PET film with a wire bar so as to givea thickness of 4 μm after drying, and then dried. Thereafter, thetemperature was raised to the isotropy transition temperature of theliquid crystal monomer, and then, the coating was gradually cooled toform a monomer layer having a uniform alignment state. The resultingmonomer layer was irradiated with UV light for fixing the alignmentstate, thereby obtaining a birefringent layer. The birefringent layerhad an in-plane retardation Re of 1 nm and a thickness directionretardation Rth of 660 nm.

Next, a 19 inch TN-mode liquid crystal monitor (LX1951D (trade name)manufactured by LG Electronics) using a commercially availablereflective polarizing plate (“D-BEF” (trade name) manufactured by 3MCompany) was disassembled. The birefringent layer was transferred fromthe PET film to the surface of the backlight-side absorptivelinearly-polarizing plate of the liquid crystal panel with a transparentacryl-based pressure-sensitive adhesive. Thereafter, a transmissiveliquid crystal display was obtained by reassembling.

Example 2

A transmissive liquid crystal display was obtained using alight-diffusing pressure-sensitive adhesive which was prepared bypreviously dispersing sphere particles of silicone with a particle sizeof 4.2 μm as the acryl-based pressure-sensitive adhesive used intransferring of the birefringent layer to the surface of the polarizingplate in Example 1.

The brightness and the contrast characteristics of each of thetransmissive liquid crystal display of Example 1 and the transmissiveliquid crystal display before the addition of the birefringent layerwere evaluated using “ConoScope” manufactured by AUTRONIC-MELCHERS GmbH.The results are shown in FIGS. 9 and 10. A comparison between them showsthat according to the invention, black brightness is reduced at obliqueviewing angles, namely light leakage is reduced.

Application to VA Mode Liquid Crystal Cell Example 3

To a reaction vessel (500 mL) equipped with a mechanical stirrer, aDean-Stark apparatus, a nitrogen-introducing tube, a thermometer, and acondenser tube were added 17.77 g (40 mmol) of2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropanoic dianhydride(manufactured by Clariant (Japan) K.K.) and 12.81 g (40 mmol) of2,2-bis(trifluoromethyl)-4,4′-diaminobiphenyl (manufactured by WakayamaSeika Kogyo Co., Ltd.). Subsequently, a solution in which 2.58 g (20mmol) of isoquinoline is dissolved in 275.21 g of m-cresol was added tothe reaction vessel, and the mixture was stirred (600 rpm) at 23° C. for1 hour to give a uniform solution. The reaction vessel was then heatedwith an oil bath so that the temperature of the inside of the reactionvessel reached 180, and the mixture was stirred for 5 hours with thetemperature maintained, resulting in an yellow solution. After thesolution was further stirred for 3 hours, heating and stirring werestopped, and the product was allowed to cool to room temperature so thata polymer was precipitated in the form of a gel.

Acetone was added to the yellow solution in the reaction vessel so thatthe above gel was completely dissolved to prepare a diluted solution (7%by weight). The diluted solution was gradually added to 2 L of isopropylalcohol under stirring to give a white powder precipitate. The powderwas separated by filtration and then added into 1.5 L of isopropylalcohol for washing. After the same process was performed once again towash, the powder was separated again by filtration. In an aircirculation type thermostatic oven, the powder was dried at 60° C. for48 hours and then dried at 150° C. for 7 hours to give a powder ofpolyimide represented by structural formula (1) below (85% yield). Thepolyimide had a weight average molecular weight (Mw) of 124,000 and animidation rate of 99.9%.

The polyimide powder was dissolved in methyl isobutyl ketone to preparea 15% by weight of polyimide solution. This solution wasunidirectionally applied to the surface of a 75 μm-thick polyethyleneterephthalate film (Lumirror S27-E (trade name) manufactured by TorayIndustries, Inc.) with a comma coater. The coating was then dried in anair circulation type drying oven at 120° C. so that the solvent wasevaporated. The above polyethylene terephthalate film was then separatedso that a 5 μm-thick birefringent layer made of polyimide was obtained.This birefringent layer had an in-plane retardation Re of 1 nm and athickness direction retardation Rth of 2000 nm.

A 20 inch VA-mode liquid crystal television (“KDL-20J3000” (trade name)manufactured by Sony Corporation) using a commercially availablereflective polarizing plate (“D-BEF” (trade name) manufactured by 3MCompany) was disassembled. Three sheets of the polyimide birefringentlayer were laminated and bonded to the surface of the backlight-sideabsorptive linearly-polarizing plate of the liquid crystal panel with atransparent acrylic pressure-sensitive adhesive. Thereafter, atransmissive liquid crystal display was obtained by reassembling thecomponents of the liquid crystal television. Here, the birefringentlayer of the three sheets of polyimide birefringent layers bonded to oneanother had an in-plane retardation Re of 3 nm and a thickness directionretardation Rth of 600 nm.

Example 4

A transmissive liquid crystal display was obtained in the same manner asin Example 3, except that a laminate of five sheets of the polyimidebirefringent layer was used in place of the laminate of three sheets ofthe polyimide birefringent layer. Here, the birefringent layer of thefive sheets of polyimide birefringent layers bonded to one another hadan in-plane retardation Re of 5 nm and a thickness direction retardationRth of 1,000 nm.

Example 5

A transmissive liquid crystal display was obtained in the same manner asin Example 3, except that a laminate of ten sheets of the polyimidebirefringent layer was used in place of the laminate of three sheets ofthe polyimide birefringent layer. Here, the birefringent layer of theten sheets of polyimide birefringent layers bonded to one another had anin-plane retardation Re of 10 nm and a thickness direction retardationRth of 2,000 nm.

Example 6

A transmissive liquid crystal display was obtained in the same manner asin Example 3, except that a laminate of 15 sheets of the polyimidebirefringent layer was used in place of the laminate of three sheets ofthe polyimide birefringent layer. Here, the birefringent layer of the 15sheets of polyimide birefringent layers bonded to one another had anin-plane retardation Re of 15 nm and a thickness direction retardationRth of 3,000 nm.

Example 7

A transmissive liquid crystal display was obtained in the same manner asin Example 3, except that a laminate of 20 sheets of the polyimidebirefringent layer was used in place of the laminate of three sheets ofthe polyimide birefringent layer. Here, the birefringent layer of the 20sheets of polyimide birefringent layers bonded to one another had anin-plane retardation Re of 20 nm and a thickness direction retardationRth of 4,000 nm.

Comparative Example 1

A transmissive liquid crystal display was obtained in the same manner asin Example 3, except that only a single piece of the polyimidebirefringent layer was used in place of the laminate of three sheets ofthe polyimide birefringent layer.

Comparative Example 2

A 20 inch VA-mode liquid crystal television (“KDL-20J3000” (trade name)manufactured by Sony Corporation) using a commercially availablereflective polarizing plate (“D-BEF” (trade name) manufactured by 3MCompany) was used as it was.

The brightness (black brightness) of the transmissive liquid crystaldisplay of each of Examples 3 to 7 and Comparative Examples 1 and 2 wasmeasured with “ConoScope” (trade name) manufactured by AUTRONIC-MELCHERSGmbH at a polar angle of 60° and azimuth angles in the range of 0 to360°. The maximum value of the brightness of each liquid crystal displayat a polar angle of 60° and azimuth angles in the range of 0 to 360° isshown in Table 1.

TABLE 1 Rth of the Birefringent Layer Brightness (nm) (cd/cm²) Example 3600 2.592 Example 4 1000 2.848 Example 5 2000 2.940 Example 6 3000 3.122Example 7 4000 2.715 Comparative Example 1 200 3.398 Comparative Example2 — 3.397

Table 1 shows that Comparative Example 1 with a low thickness directionretardation did not produce the effect of reducing black brightness,compared with Comparative Example 2 without birefringent layer, whileblack brightness was reduced at a polar angle of 60° in each Example. Asdescribed above, the liquid crystal display of the invention cansuppress light leakage in oblique directions and consequently achievehigh-contrast image display.

1. A transmissive liquid crystal display, comprising: a light source(BL), a reflective linearly-polarizing layer (Pr1), a birefringent layer(A), a light source-side absorptive linearly-polarizing layer (P1), aliquid crystal cell (LC), and a viewer-side linearly-polarizing layer(P2) which are arranged in this order and satisfy all the followingconditions: (a) transmission axes of the reflective linearly-polarizinglayer (Pr1) and the light source-side absorptive linearly-polarizinglayer (P1) are arranged substantially parallel to each other; (b) saidbirefringent layer has a thickness direction retardation Rth whichsatisfies the relation 250 nm≦Rth≦6000 nm; and (c) of linearly polarizedlight emitted from the light source (BL) and transmitted through thereflective linearly-polarizing layer (Pr1), the birefringent layer (A)makes substantially no change in the polarization state of linearlypolarized light in the normal direction while the birefringent layer (A)makes a change in the polarization state of linearly polarized light inan oblique direction.
 2. The transmissive liquid crystal displayaccording to claim 1, wherein said birefringent layer (A) has anin-plane retardation Re of from 10 nm to 100 nm, and a slow axis of thebirefringent layer (A) and a transmission axis of the reflectivelinearly-polarizing layer (Pr1) are substantially parallel orperpendicular to each other.
 3. The transmissive liquid crystal displayaccording to claim 1, wherein said birefringent layer (A) has anin-plane retardation Re of 20 nm or less.
 4. The transmissive liquidcrystal display according to claim 1, wherein said birefringent layer(A) has an in-plane retardation Re and a thickness direction retardationRth which satisfy the relation: 400 nm≦Rth−2×Re≦800 nm.
 5. Thetransmissive liquid crystal display according to claim 1, comprising areflective linearly-polarizing layer (Pr2) between said birefringentlayer (A) and said light source-side absorptive linearly-polarizinglayer (P1) in such a manner that the light source-side absorptivelinearly-polarizing layer (P1) and the transmission axes are parallel toeach other.
 6. The transmissive liquid crystal display according toclaim 1, comprising a light source-side light-diffusing layer (D1)between said birefringent layer (A) and said light source-sideabsorptive linearly-polarizing layer (P1).
 7. The transmissive liquidcrystal display according to claim 1, comprising a viewer-sidelight-diffusing layer (D2) on the viewer side from the viewer-sidelinearly-polarizing layer (P2).
 8. The transmissive liquid crystaldisplay according to claim 1, wherein said reflectivelinearly-polarizing layer (Pr1), said birefringent layer (A) and saidlight source-side absorptive linearly-polarizing layer (P1) areintegrally bonded to one another with a pressure-sensitive adhesive. 9.A laminated polarizing plate for use in the transmissive liquid crystaldisplay according to claim 1, comprising a reflectivelinearly-polarizing layer (Pr1), a birefringent layer (A) and a lightsource-side absorptive linearly-polarizing layer (P1) which are arrangedin this order.
 10. A polarized light source device for use in thetransmissive liquid crystal display according to claim 1, comprising alight source (BL), a reflective linearly-polarizing layer (Pr1), abirefringent layer (A), and a light source-side absorptivelinearly-polarizing layer (P1) which are arranged in this order.